Fuel injection apparatus for externally ignited internal combustion engines operating on continuously injected fuel

ABSTRACT

In a fuel injection apparatus the air-fuel ratio is controlled by an air sensor as a function of the air quantities passing through the suction tube. Said ratio is varied by altering a liquid pressure which serves as a return force for the air sensor. The liquid pressure is varied by a valve loaded in the closing direction by a spring, the bias of which is affected, among others, during the warm-up run of the engine, by the pressure that prevails in the suction tube immediately downstream of an arbitrarily operable butterfly valve.

United States Fatent n91 Ecltert et a1.

[451' Feb. '12, 1974 1 FUEL INJECTION APPARATUS FOR EXTERNALLY lGNITED INTERNAL COMBUSTION ENGINES OPERATING ON CONTINUOUSLY INJECTED FUEL [75] Inventors: Konrad Eckert, Stuttgart; Heinrich Knapp, Leonberg-Silberberg, both of Germany [73] Assignee: Robert Bosch GmbH, Stuttgart,

Germany [22] Filed: Nov. 24, 1972 [21] Appl. No.: 308,986

[30] Foreign Application Priority Data Nov. 24, 1971 Germany 2158093 [52] US. Cl..... 123/119 R, 123/139 AW, 261/50 A [51] Int. Cl. F02m 69/00 [58] Field of Search. 123/119 R, 139 AW, 140 MC, 123/140 CC, 140 MP; 261/50 A, 50 AA, 39

[56] 7 References Cited UNITED STATES PATENTS 3,680,535 8/1972 Eckert et al. 123/119 R 3,730,155 5 1973 Knapp 123/119 R Primary Examiner-Wendell E. Burns Attorney, Agent, or FirmEdwin E. Greigg [57] ABSTRACT In a fuel injection apparatus the air-fuel ratio is controlled by an air sensor as a function of the air quantities passing through the suction tube. Said ratio is varied by altering a liquid pressure which serves as a return force for the air sensor. The liquid pressure is varied by a valve loaded in the closing direction by a spring, the bias of which is affected, among others, during the warm-up run of the engine, by the pressure that prevails in the suction tube immediately downstream of an arbitrarily operable butterfly valve.

4 Claims, 2 Drawing Figures PAIENIE FEB 1 2mm SHEET 1 BF 2 memes-FEM 2 4 I 3,791,359

SHEET 2 [1F 2 Fig.2

FUEL INJECTION AIPARATUS FOR EXTERNALLY IGNITEI) INTERNAL COMBUSTION ENGINES OPERAG ON CONTINUOUSLY INJECTED FUEL BACKGROUND OF THE INVENTION This invention relates to a fuel injection apparatus serving an externally ignited internal combustion engine which operates on fuel that is continuously injected into the suction tube (air intake pipe) of the engine. The fuel injection apparatus is of the type which has in the suction tube an arbitrarily operable butterfly valve arranged spaced from an air sensor which is moved by and in proportion to the throughgoing air quantities against a return force which is substantially constant, that is, its magnitude does not change in response to the position of the air sensor. The latter, in the course of its excursion, displaces a movable component of a fuel distributor and metering valve disposed in the fuel line for metering a fuel quantity which is proportionate to the air quantities flowing in the suction tube. The afore-noted return force is supplied by liquid under pressure which is delivered continuously and under constant pressure through a pressure conduit and which exerts a force on a control plunger connected at least indirectly with the air sensor for applying a return force thereto. The pressure of said liquid is variable by a pressure control valve situated in the pressurized liquid circuit. The movable valve member of the last named valve is actuated against the force of a spring, the bias of which is variable by means of a temperature-dependent control element (expansible regulator). Immediately after starting the engine, the movable valve member is engaged by a second temperature-dependent control element for a short period of time. This type of apparatus is described in Heinrich Knapp application Ser. No. 2l2,995 filed Dec. 28, 1971, now US. Pat. No. 3,730,155 owned by the same assignee.

In a fuel injection apparatus of the afore-noted type the enrichment of the mixture for the warm-up run of the engine is multiplicative in nature and thus, during acceleration, the exhaust gases of the internal combustion engine will contain an excessive amount of pollutants. Recent Clean Air laws make the requirements regarding the optimal design of the warm-up run extremely stringent. Tests have shown that the enrichment should be constant between additive and multiplicative values and that in the acceleration phase there should be, in addition, a momentary enrichment in order to compensate for the increased condensation as the vacuum drops, until, by means of wall moistening, a reduced stationary quantity is again automatically set. With an increasing rpm the enrichment should be reduced, since the fuel preparation is improved by means of the higher air speed.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection apparatus by means of which'in the warm-up phase during acceleration the generation of an excessive percentage of pollutants in the exhaust gas of the engine is avoided.

Briefly stated, according to the invention, during the warm-up operation of the internal combustion engine the bias of the spring of the pressure control valve is additionally variable as a function of the pressure in the BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic sectional view of the fuel injection apparatus incorporating the preferred embodiment and FIG. 2 is a diagram illustrating the course of the fuel enrichment as a function of the engine performance characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIG. 1, in the fuel injection apparatus shown therein the combustion air flows in the direction of arrow A through the suction tube portion 1 and then through the conical suction tube portion 3 in which there is disposed an air sensor 2. Therefrom the air flows in a suction tube portion 4 and thereafter through a coupling hose 5 into a suction tube portion 6 in which there is disposed an arbitraily operable butterfly valve 7. From the latter the combustion air flows to one or more cylinders (not shown) of an internal combustion engine. The air sensor 2 is constituted by a plate disposed normal to the direction of air flow and is moved in the conical suction tube portion 3 as an approximately linear function of the throughgoing air quantities. Given a constant return force exerted on the air sensor 2 as well as a constant air pressure prevailing upstream of the air sensor 2, the pressure prevailing between the air sensor 2 and the butterfly valve 7 also remains constant.

The air sensor 2 directly controls a metering and fuel distributor valve llIiJFor the transmission of the motion of the air sensor 2 there serves a lever 11 which is fixedly connected with the sensor plate and is swingably supported, with the lowest possible friction, by a pivot 12. The lever 11 is provided with an integral nose 13 which actuates a movable valve component 14 forming part of the metering valve 10 and shaped as a control plunger. The radial face 15 of the control plunger 14 disposed remote from the nose 13 is exposed to the force of pressurized liquid which serves as the return force exerted on the air sensor 2.

Fuel supply is effected by means of a fuel pump 19 which is driven by an electromotor 18 and which draws fuel from a fuel tank 26 and delivers it through a conduit 21 to the fuel metering and distributor valve 10. From the conduit 21 there extends a conduit 22 in which there is situated a pressure limiting valve 23.

From the conduit 21 the fuel is admitted into a channel 26 provided in the housing of the fuel distributor and metering valve 10. The channel 26 leads to an annular groove 27 of the control plunger 14 and further leads through several branch conduits to individual chambers 28, is exposed to the fuel pressure. Dependent upon the axial position of the control plunger 14, the annular groove 27 bounded by a control edge 27a overlaps to a greater or lesser extent the control slots 31 which lead, through channels 31, to chambers 32. Each of the latter is separated from an associated chamber 28 by means of the diaphragm 29. From the chambers 32 the fuel is admitted through injection channels 33 to the individual fuel injection valves (not shown) which are positioned in the suction tube in the vicinity of the associated engine cylinder. The diaphragm 29 serves as the movable part of a flat seat this manner it is ensured that the extent of displacement of the control plunger 14 and the metered fuel quantities are proportionate to one another.

Upon a pivotal motion of the lever 11 the air sensor 3 plate 2 is moved in the conical suction tube portion 3 and, as a result, the annular flow passage section between the sensor plate and the inner wall of the cone 3 changes in proportion to the excursion of the air sensor 2. In this manner there is ensured a linear dependency between the setting motion of the air sensor 2 and the displacement of the control plunger 14 and thus, accordingly, there is ensured a proportionate fuel metering.

The pressurized liquid which exerts a return force on the air sensor 2 through the control plunger 14'is fuel. For this purpose, from the conduit 21 there extends a conduit 37 which opens into a pressure chamber 38 into which projects that terminus of the control plunger 14 which contains the radial face 15. In the conduit 37 there is disposed a throttle 39 which separates the fuel supply circuit 21 associated with the fuel metering valve 10 from the control pressure circuit 37, 40 associated with a pressure control valve 41 now to be described.

From the conduit 37, downstream of the throttle 39, there extends a conduit 40 to the pressure control valve 41. From the latter there extends back to the fuel tank a depressurized return conduit 42. During the warm-up run of the internal combustion engine, the pressure of the liquid that serves as the return force is controlled in a temperature-dependent manner by means of the pressure control valve 41. The latter is formed as a flat seat valve having a stationary valve seat 43 and a diaphragm 44 which is loaded in the closing direction of the valve by a spring 45.

The chamber 46 accommodating the spring 45 forms a part of a bypass conduit 48, 49 which circumvents the butterfly valve 7. The said bypass conduit is shown in FIG. 1 only by its coupling points at the suction tube and at the pressure control valve 41. The chamber 46 further accomodates a piston plunger 50 which controls the flow passage section of the bypass conduit 48, 49 and which also serves as a spring seat disc for the spring 45.

The piston plunger 50 is shifted by a temperaturedependent control element (expansible regulator) 52 which, when the internal combustion engine is cold, compresses the spring 45 to a lesser extent than in the case of a warm engine. Also, the piston plunger 50 opens the bypass conduit 48, 49 to a greater extent when the engine is cold than when it is in a warm condition. That terminus of the spring 45 which is remote from the piston plunger 50 is in engagement with a spring seat disc 53 which exerts a force on the memberane 44 through an intermediate member 54. Thus, when the combustion engine is cold, the load exerted on the diaphragm by the spring 45 is smaller and consequently more pressurized liquid flows through the valve 43 and 44 As a result, the pressure of the fuel operating as the return force in the chamber 38 is smaller and the ratio of the injected fuel quantity to the air quantities is larger than in case of a warm engine.

The spring disc seat 53 has at its side oriented away from the spring 45, a recess 55 into which projects one terminus of a bi-metal spring 56. The other terminus of the latter is surrounded by a heater element 57 which, together with the bi-metal spring 56, constitutes a second temperature-dependent control element 56, 57. The heater element 57 is connected in the electric network of the vehicle in such a manner that it is energized when the ignition is turned on. The bi-metal spring 56 is engaged by an actuating member 59 which is fixedly connected with the diaphragm 60 of an aneroid 61. The latter is connected by means of a conduit 62 with the suction tube at a location downstream of the butterfly valve 7. The conduit 62 contains an adjustable throttle 63. In FIG. l the components are shown in their position when the engine is cold. It is seen that when the engine is cold, a rivet 64 secured to the bimetal spring 56 engages the spring seat disc 53.

The pressurization of the pressure chamber 38 is ef fected through a throttle 67 which serves as a damping means.

OPERATION OF THE PREFERRED EMBODIMENT When the internal combustion engine is running, fuel is drawn from the tank 20 by the pump 19 driven by the electromotor 18 and forced through the conduit 21 to the fuel metering valve 10. At the same time the internal combustion engine draws air through the suctiontube and, as a result, the air sensor 2 undergoes a certain excursion from its position of rest. In response to the deflection of the air sensor 2 the control plunger 14 is displaced towards the right by the counterclockwise pivoting lever II and thus the flow passage section at the control slot 30 is increased. The direct connection between the air sensor 2 and the control plunger 14 ensures a constant ratio between the air quantities and the metered fuel quantities provided the characteristics of these two components are sufficiently linear (which is desideratum by itself). In such a case then the air-fuel ratio would be constant for the entire operational range of the engine. It is, however, a requirement that dependent upon the operational conditions of the internal combustion engine, the air-fuel mixture be richer or leaner which is, in turn, achieved by altering the return force affecting the airsensor 2.

Since the magnitude of the load on the engine is characterized, among others, by the position of the butterfly valve 7, the return force is expediently altered as a function of the position of the butterfly valve by means of a pressure control valve (not shown).

Disregarding first the effect of the control element 56, 57, in case of a cold internal combustion engine an enrichment of the fuel in the fuel-air mixture will be achieved by virtue of the expansible regulator 52 associated with the pressure control valve 41. As noted earlier, such an enrichment takes place because the pressure of the liquid which serves as the return force affecting the air sensor 2 is reduced in the pressure chamber 38. The piston plunger 50displaced by means of the expansible regulator 52, maintains the bypass conduit 48,49 open in this operational condition of the engine. In this manner, during the starting of the cold engine, there is achieved a greater flow rate of the air-fuel mixture to compensate for the relatively large frictional resistances in a cold engine.

The first temperature-dependent control element (expansible regulator) 52 responding to the coolant temperature begins to reduce the fuel enrichment by compressing the spring 45 and thus increasing the control pressure on the control plunger 14 with a relatively long delay. Since, however, already a short time after the engine start, the cylinder walls are preheated by virtue of the preceding ignitions and thus fuel condensation caused by the previously cold cylinder walls is progressively reduced, it is expedient to reduce the fuel enrichment to such an extent that thereafter a clean run of the internal combustion engine is ensured. For this purpose the bimetal spring 56, normally working against the spring 45 after reaching a certain temperature, bends out of contact with the spring seat disc 53,

whereby the entire force of the spring 45 is available for controlling the return force affecting the air sensor and thus reducing fuel enrichment. The spring 45 is also opposed by a force which depends upon the pressure prevailing downstream of the butterfly valve 7 in the suction tube. For this purpose, a force-transmitting rod 59 affixed to the diaphragm 60 of the aneroid 61 is connected with the bimetal spring 56. The aneroid 61 communicates through a conduit 62, having a throttle 63, in such a manner with the suction tube downstream of the butterfly valve 7 that approximately beyond a position of 10 of the butterfly valve this pressure becomes substantially ineffective. As the bimetal spring 56 progressively bends away from the spring seat disc 53 by virtue of the effect of the heater 57, the pressure in the suction tube also loses its effect so that in case of an entirely withdrawn bimetal spring the force of the aneroid 61 is insufficient to press the bimetal spring against the spring seat disc 53.

The fuel enrichment during the warm-up run of the engine will now be explained in more detail with reference to FIG. 2 which illustrates the fuel enrichment A as a function of the engine performance graph, Q is the fuel quantity per stroke and n is the rpm of the internal combustion engine. The dashed curve a represents the conventional multiplicative and rpm-independent enrichment which depends from the bias of the spring 45. According to the invention, for full load, the enrichment is to be reduced to half of its value, while for idling it is to be maintained at its original value. For this purpose the multiplicative enrichment is first reduced to one half of its value in accordance with the dashdotted curve b. Thus, the force exerted by the aneroid 61 is so designed that during idling the pressure prevailing in the suction tube downstream of the butterfly valve 7 causes an enrichment of original valve as indicated at point B. Since. as the load increases, the presence in the suction tube downstream of the butterfly valve also increases. there is obtained, as desired, the characteristic solid line curve c which is half additive and half multiplicative.

As the load increases there is, in the first moment, an enrichment beyond the curve 0 in accordance with the dashed curve a, since the vacuum prevailing during idling and during partial load conditions downstream of the butterfly valve 7 in the suction tube, caused an evacuation of the aneroid 61 and there is needed a certain period of time for its recharge through the throttle 63. Subsequent to this period which may be adjusted by varying the throttle diameter or the volume of the aneroid box, the level of enrichment returns to the curve C. 1n this manner it is ensured that during load increase there is a temporary enrichment in order to compensate for the increased condensation as the vacuum is reduced, until, by virtue of wall moistening, the reduced stationary fuel quantity is automatically reestablished.

The rpm dependence of the pressure in the aneroid 61 is achieved by tapping the suction tube pressure at an approximately 10 position of the butterly valve 7. Since by virtue of this arrangement of the conduit 62 the effect of the suction tube pressure at larger angles of the butterfly valve is progressively reduced, the aforenoted effect will prevail only in the range below the 10 characteristic curve d of the engine performance graph. Since the 10 characteristic curve approximates zero at higher rpms, a pressure effect is no longer present at higher 'rpms, so that there the decreased multiplicative enrichment is achieved according to the curve b.

What is claimed is:

1. In a fuel injection apparatus serving an externally ignited internal combustion engine operatingon fuel continuously injected into the suction tube of the engine, said engine having an arbitrarily operable butterfly valve situated in said suction tube, said fuel injection apparatus being of the known type that has (a) an air sensor situated in said suction tube, said air sensor being deflected by and as a function of the air quantities flowing through said suction tube, (b) a control plunger operatively connected with said air sensor, (0) a pressurized liquid circuit for exposing said control plunger to liquid pressure to cause said control plunger to exert a return force on said air sensor in opposition to the deflecting force exerted thereon by said air quantities, said return force being independent from the position of saidcontrol plunger, (d) means for continuously supplying said pressurized liquid circuit with pressurized liquid, (6) a pressure control valve situated in said pressurized liquid circuit for controlling the liquid pressure affecting said control plunger, said pressure control valve having a movable valve member, (I) a spring forming part of said pressure control valve and loading said movable valve member, (g) a first temperature-dependent control element connected to said spring for varying the bias thereof, (h) a second temperature-dependent control element affecting said movable valve member for a short period immediately after engine start and (i) a fuel metering and distributor valve having a movable component displaceable by said air sensor for metering fuel in proportion to said air quantities flowing through said suction tube, the improvement comprising means for additionally varying the bias of said spring during the warm-up run of the engine as a function of the pressure in said suction tube downstream of said butterfly valve.

2. An improvement as defined in claim 1, including A. a bimetal spring connected with said movable C. an aneroid having a chamber and a diaphragm an adjustable throttle disposed in said conduit means means bounding Said C mber, for arbitrarily varying the pressure in the latter.

D, conduit means for maintaining communication 4 A i v nt as defined in claim 1, including between said chamber of said aneroid and a locabypass conduit means communicafing with km} tion of said suction tube downstream of said buttertions upstream and downstream of said butterfly fly valve and valve, and

E. force-transmitting means connecting the diaphragm of said aneroid to said bimetal spring; said aneroid, said conduit means and said forcetransmitting means constituting said means for ad- 10 ditionally varying the bias of said spring of said pressure control valve.

3. An improvement as defined in claim 2, including B. closing means connected and responsive to said first temperature-dependent control element, said closing means cooperating with said bypass conduit means to close the latter when said engine reaches normal operating temperatures. 

1. In a fuel injection apparatus serving an externally ignited internal combustion engine operating on fuel continuously injected into the suction tube of the engine, said engine having an arbitrarily operable butterfly valve situated in said suction tube, said fuel injection apparatus being of the known type that has (a) an air sensor situated in said suction tube, said air sensor being deflected by and as a function of the air quantities flowing through said suction tube, (b) a control plunger operatively connected with Said air sensor, (c) a pressurized liquid circuit for exposing said control plunger to liquid pressure to cause said control plunger to exert a return force on said air sensor in opposition to the deflecting force exerted thereon by said air quantities, said return force being independent from the position of said control plunger, (d) means for continuously supplying said pressurized liquid circuit with pressurized liquid, (e) a pressure control valve situated in said pressurized liquid circuit for controlling the liquid pressure affecting said control plunger, said pressure control valve having a movable valve member, (f) a spring forming part of said pressure control valve and loading said movable valve member, (g) a first temperature-dependent control element connected to said spring for varying the bias thereof, (h) a second temperaturedependent control element affecting said movable valve member for a short period immediately after engine start and (i) a fuel metering and distributor valve having a movable component displaceable by said air sensor for metering fuel in proportion to said air quantities flowing through said suction tube, the improvement comprising means for additionally varying the bias of said spring during the warm-up run of the engine as a function of the pressure in said suction tube downstream of said butterfly valve.
 2. An improvement as defined in claim 1, including A. a bimetal spring connected with said movable valve member, B. a heater connected with said bimetal spring for heating the latter immediately after engine start, said bimetal spring and said heater constituting said second temperature-dependent control element, C. an aneroid having a chamber and a diaphragm means bounding said chamber, D. conduit means for maintaining communication between said chamber of said aneroid and a location of said suction tube downstream of said butterfly valve and E. force-transmitting means connecting the diaphragm of said aneroid to said bimetal spring; said aneroid, said conduit means and said force-transmitting means constituting said means for additionally varying the bias of said spring of said pressure control valve.
 3. An improvement as defined in claim 2, including an adjustable throttle disposed in said conduit means for arbitrarily varying the pressure in the latter.
 4. An improvement as defined in claim 1, including A. bypass conduit means communicating with locations upstream and downstream of said butterfly valve, and B. closing means connected and responsive to said first temperature-dependent control element, said closing means cooperating with said bypass conduit means to close the latter when said engine reaches normal operating temperatures. 